Roasting coffee is complex.
Many changes occur when green coffee is roasted. The Maillard Reaction causes green coffee to turn yellow before darkening to brown. This is the reaction that occurs between reducing sugars and amino acids to produce fragrance and flavour.
As the roasting process continues, the moisture in the beans begins to evaporate. This energy builds up and bursts outward, causing the beans to fracture. The beans then double in size and lose a fifth of their weight as they shed a coat of skin known as chaff. As we roast beyond the first crack, we can create and intensify various flavours.
As with a lot of things when it comes to coffee, it’s a personal preference as to how much we let the coffee develop and roast, changing the result and overall experience.
Light Roasts
Beans that are lightly roasted appear dry and pale in general (usually a very light brown). They’ve been subjected to less heat and therefore less change, meaning they’re likely to retain a greater amount of their original qualities, whether that’s fruitiness, nuttiness or other complex notes that come from the coffee plant.
- Higher levels of acidity
- Low levels of bitterness
- May offer a delicate balance of complex flavours
- Retains its natural aroma
- Offers less body (thickness) than darker roasts
Medium roast
Medium-roasted beans have a significantly sweeter taste in general than light roasts. While some of the bean’s natural characteristics will be enhanced, others may be diminished, such as acidity and specific coffee flavours.The roasting procedure will also impart additional flavours, such as sweetness, to these beans.
They will still feel dry to the touch and less oily than dark roasted beans, but lengthier roasting will bring more taste from the process (sweetness) while removing some of the inherent bean qualities (acidity and coffee overtones).
Dry to the touch and usually mid-brown in colour, medium roast beans also offer a fuller body with some bitterness to the cup, depending on how far down the road they are. It’s a popular option for many specialty coffee beans offering a good balance of acidity, original flavour and sweetness.
- Mild yet present levels of acidity
- A good amount of flavour nuance and complexity from the original beans
- Higher levels of sweetness without being overwhelming
- Medium level of bitterness, often counterbalanced by other characteristics
- Moderate level of body
Dark Roasts
Dark-roasted beans have seen the largest chemical changes. Any intrinsic characteristics are typically lost and replaced with features arising from the roasting process, such as increased bitterness and body.
If you are starting with low-quality coffee beans with few or no identifying qualities, the masking effect is not always harmful.People enjoy full-bodied bitter coffees made from relatively common beans, as proven by the success of several prominent coffee chains.
- Minimal levels of acidity
- High levels of bitterness
- Few delicate nuances of flavour
- Reduced sweetness
- Potentially more savoury notes such as chocolate or liquorice
- A heavier body and sometimes more powerful aftertaste
You should feel free to make up your own mind about what tastes better, but there are a few reliable pairing suggestions that might help you choose the right brew method to match your coffee roast, or the other way around
| Roast Type | Brew Methods |
| Light roasts | Filter (V60, Chemex) |
| Medium roasts | Espresso, French Press, Aeropress, Moka Pot, Filter (V60, Chemex) |
| Darker roasts | Espresso, French Press, Aeropress, Moka Pot |
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(What Color is Your Coffee? | 25, Issue 21, n.d.)
